Relationship between exercise hyperpnea, hemodynamics, and blood gases before and during glyceryl trinitrate infusion in patients with exercise-induced elevation of pulmonary artery wedge pressure

Effects of isosorbide dinitrate on electrocardiography, hemodynamics, and ventilation in patients with exercise-induced elevation of pulmonary artery wedge pressure

BACKGROUND

The mechanisms underlying exertional hyperpnea in patients with coronary artery disease and transient left ventricular dysfunction are still not fully understood.

HYPOTHESIS

The study was undertaken to investigate whether the ventilatory response to exercise reflects the effects of acute medical treatment of exercise-induced left ventricular dysfunction, and to evaluate mechanisms relevant to excessive exertional ventilation.

METHODS

In 11 male patients, aged 65.2 +/- 6.0 years, all with pulmonary artery wedge pressure (PAWP) > 25 mmHg and ST depression > 2 mm during moderate supine exercise, ventilation (V), oxygen uptake (VO2), hemodynamics, electrocardiogram (ECG), and arterial and mixed venous blood gases were examined during supine rest and exercise, before and at hourly intervals after peroral intake of 30 mg isosorbide dinitrate (ISDN). Six similar patients were examined with the same protocol without ISDN administration and comprised a control group.

RESULTS

Before administration of ISDN, exercise PAWP was 35.3 +/- 5.9 mmHg, ECG showed 2.77 +/- 1.06 mm ST depression, and V/VO2 was 31.8 +/- 4.8 l/l. One h after ISDN administration, exercise mean PAWP was 11.0 +/- 2.5 mmHg (p < 0.001), ST depression 0.59 +/- 0.8 mm (p < 0.001), whereas V/VO2 was unchanged, 30.1 +/- 5.3 l/l. Two h later, PAWP remained reduced and there were only minor ST depressions, while V/VO2 remained high. Exercise cardiac index (CI) and mixed venous oxygen tension (PvO2), initially 4.7 +/- 0.67 l/min/m2 and 3.54 +/- 0.35 kPa, respectively, remained at the same low level throughout the study. In the six nontreated patients, there were no significant changes in ST depression, exercise PAWP, or exertional ventilation.

CONCLUSION

Isosorbide dinitrate treatment markedly improved exercise-induced left heart dysfunction, whereas excessive ventilatory response was unaffected, even after 3 h. Thus, measurements of the exercise hyperpnea did not properly reflect effective reduction of myocardial ischemia.

Excessive exercise ventilation in moderate left heart dysfunction. Influence of postural changes in central haemodynamics and blood gases

To evaluate the relative importance of pulmonary congestion and peripheral hypoxia as causes for the excessive exercise ventilation in left heart dysfunction, seven patients with excessive ventilation and distinct left heart dysfunction during moderate exercise (LHD), and seven control patients with essentially normal exertional functions (CTR), had ventilation, central haemodynamics, arterial and mixed venous blood gases examined at rest and exercise, 32 W (25-40) in the LHD group and 44 W (33-49) in the CTR group, in lying and sitting positions. Change from lying to sitting exercise, led to fall in pulmonary artery wedge pressure (PAWP) from 31.0 +/- 5.5 to 8.8 +/- 5.0 mmHg in the LHD group, compared with from 13.7 +/- 1.0 to 2.1 +/- 2.4 mm Hg in the controls, while ventilation/O2 intake ratio (V/VO2) and physiological dead space/tidal volume ratio (VD/VT) showed a tendency to rise, from 36.3 +/- 8.8 to 39.2 +/- 7.4, and from 0.35 +/- 0.11 to 0.39 +/- 0.09, respectively, in the LHD group, and from 27.5 +/- 3.1 to 28.7 +/- 5.3, and from 0.19 +/- 0.09 to 0.21 +/- 0.12 in the controls. Mixed venous O2 tension (PvO2) showed a marked decline from 3.60 +/- 0.33 to 3.26 +/- 0.36 kPa in the LHD group, as compared with from 3.94 +/- 0.28 to 3.71 +/- 0.29 kPa in the controls, while the calculated physiologic shunt (Qs/Qt) suggested improved alveolo-arterial gas exchange. The data fit in with recent studies ascribing the excessive exercise ventilation to a combination of signals from hypoxia-induced changes, particularly in the exercising muscles, and augmented ergoreflex and central and peripheral chemoreceptor activity, partly to changes in the integrated control of ventilation and circulation, not to mechanisms related to pulmonary congestion.

Delayed respiratory response to exercise of short duration in patients with severe intermittent claudication due to bilateral atherosclerotic vascular disease: normalization after aorto-bifemoral bypass operation

To investigate the respiratory response to exercise in patients with severe intermittent claudication, eight male patients, aged 57 years (range 43-73), with bilateral multi-segment atherosclerotic vascular disease, median maximum walking distance 50 m (range 20-200) and ankle-to-arm pressure index 0.4 (range 0.3-0.6), were studied before and after aorto-bifemoral bypass operation. Ventilation, CO2 output and O2 intake were recorded in the sitting position during 20 min of rest, 1 min of leg exercise on a bicycle ergometer [4.9 kJ (500 kpm)], and 20 min of recovery and rest. Before operation, maximal ventilation and CO2 output per minute were observed 2-4 min after cessation of work, while afterwards peak values were found during the work or the first minute of recovery. Pre-operatively, the extra ventilation and CO2 output during the work and recovery period and the recovery times of the ventilation and CO2 output per minute were markedly increased. Afterwards these values were clearly reduced towards normal. It is concluded that patients with severe intermittent claudication show a characteristic delay and prolonged rise in the respiratory response to exercise of short duration, which closely corresponds to the previously described pattern of outflow of hypoxia-generated metabolites from the exercising muscles. The pattern of respiratory response after operation reflects the fact that these patients also suffer from atherosclerotic heart dysfunction.